The present invention relates to a sliding vane type rotary compressor which is used, for example, in an automobile air conditioner.
The current demand for energy saving has given rise to the demand for higher efficiency compressors for use in refrigerating cycles. In particular, compressors used in car air conditioners encounter the following problems: namely, (1) refrigerating capacity becomes excessively large during high-speed operation due to the fact that the compressor is forcibly driven by an associated engine at speeds proportional to the engine speed, and (2) the heat load condition on a heat exchanger varies largely in accordance with changes in the environmental condition and running condition of the automobile on which the compressor is mounted.
In order to ensure an adequate refrigerating conditions by overcoming these problems peculiar to air conditioners, methods have been proposed for allowing control of the volume displacement of the compressor from the outside.
One of such methods is to release compression of gases by disengaging a delivery valve from the cylinder of the compressor by means of a solenoid valve. This method, however, requires a large space where the solenoid valve is mounted, so that it results in large overall size and an increased total weight of the compressor, as well as complications in the construction of the compressor. In addition, a careful selection of the materials is required in order to maintain a stable state of bonding between the coils of the solenoid which builds up heat under severe conditions of high temperatures and pressures, which in turn makes it difficult to fabricate the solenoid and raises the production cost.